Finishing hollow blow molded articles

ABSTRACT

A method for finishing a blow molded plastic article having flash attached to a neck portion thereof which includes gripping and relatively moving the flash and the article away from each other to sever the flash at a portion immediately adjacent the end of the neck which is at an elevated temperature with respect to the neck portion, and thereafter advancing a forming mandrel into the neck to roll an irregular edge left in the area of flash severance forwardly toward the body of the article and outwardly against the wall of the neck to form a smooth finish. The apparatus includes an inwardly directed step in the blow mold at the extremity of the neck defining portion of the mold whereat a thickened and therefore elevated temperature portion of the plastic is formed on expanding the parison, this thickened section being the area where severing occurs during finishing.

United States Patent Reilly [451 Nov. 5, 1974 [54] FINISHING HOLLOW BLOWMOLDED 3,417,428 12/1968 Rupert 264/94 X ARTICLES 3,429,211 2/1969 Pelot83/914 X Inventor: Joseph R. Reilly, Navgatuck, Conn. Assignee: MonsantoCompany, St. Louis, Mo.

Filed: Oct. 19, 1972 Appl. No.: 299,007

Related US. Application Data Division of Ser. No. 120,514, March 3,1971, Pat. No. 3,736,091.

US. Cl 264/161, 264/89, 264/98, 264/163, 264/296, 264/296, 264/323,264/327, 425/D1G. 215, 425/D1G. 806

Int. Cl. B29c 17/07, B290 17/12 Field of Search 264/89, 90, 98, 99, 161,264/163, 162, 296, 327, 320, 322, 323; 425/D1G. 806, 326, 387, DIG. 204,DIG.

References Cited UNITED STATES PATENTS 1/1941 Ferngren 264/98 8/1961Schaich 264/161 X 12/1965 Budesheim 264/98 X 2711111 7111/ If, H b

Primary Examiner-Jan H. Silbaugh Attorney, Agent, or Firm-Michael J.Murphy [57] ABSTRACT A method for finishing a blow molded plasticarticle having flash attached to a neck portion thereof which includesgripping and relatively moving the flash and the article away from eachother to sever the flash at a portion immediately adjacent the end ofthe neck which is at an elevated temperature with respect to the neckportion, and thereafter advancing a forming mandrelinto the neck to rollan irregular edge left in the area of flash severance forwardly towardthe body of the article and outwardly against the wall of the neck toform a smooth finish. The apparatus includes an inwardly directed stepin the blow mold at the extremity of the neck defining portion of themold whereat a thickened and therefore elevated temperature portion ofthe plastic is formed on expanding the parison, this thickened sectionbeing the area where severing occurs during finishing.

PATENTEIJIDV sum I SIEEI2G3 FIG. 4

This is a division of application Ser. No. 120,514, filed Mar. 3, 1971now US. Pat. No. 3,736,091.

BACKGROUND OF THE INVENTION This invention relates to the finishing ofblown hollow articles and more particularly to forming smooth neckfinishes on such articles either inside or outside of the forming mold.

When hollow articles having neck portions at one end are formed byexpanding a heat softened tubular parison within a blow mold, anappendage known as waste flash may be left attached to the neck portionas a result of the molding operation, which must be removed before thearticle can be considered ready for use. In the past, this has been doneby machinery downstream of the molding station incorporating a saw forcutting off the flash just above or at the end of the neck and a highspeed reaming tool for drilling away the remaining flash to finish theneck surface sufficiently smoothly as to provide an aestheticallyappealing end on the article and/or to permit flush fitting of a closurethereon when the article, for example, is a bottle. Such finishing isalso necessary to eliminate any sharp surfaces on the inner surface ofthe neck when the article is a bottle out of which the contents might beconsumed directly by a user. Needless to say, in high throughput,continuously operating molding lines, such tooling becomes dull ratherfrequently, necessitating equipment downtime for tooling replacement andrequiring labor' for resharpening. The situation is aggravated when theworkpiece is formed from a plastic which is relatively hard and brittle,such as those formed from high nitrile group containing materialswherein the plastic comprises at least 60weight percent of a polymerformed from a nitrile group containing monomer. Also, special handlingof the article may be required between the mold and the trimmingmachinery to permit finishing in an upside down position to insurethat-plastic particles, e.g., in the form of chips, do not end up in thebody of the article. This latter situation is especially critical whenthe article is a container in the form of a bottle for holding aconsumable product.

Alternative approaches for finishing the neck portion of a blown hollowarticle have involved manipulating the end of the heat softened parisonfrom which the article is formed while it is disposed within the cavityof the blow mold, and generally either before or during expansion toform the article. Techniques for accomplishing this are disclosed in anumber of issued U.S. Pats. e.g., US. Pat. Nos. 3,272,896; 3,303,249 and3,410,937. Such systems, however, suffer the common deficiency ofrelying for parison support on an inwardly extending projection in theneck area of the mold, which is meant to close upon and frictionallyengage the outer surface of the parison as the mold sections cometogether. This has been found difficult to consistently accomplish,realizing that the outside diameter of the parison is purposely beingkept less than that of the diameter of the mold neck portion, since thisis essential in order to avoid generating more flash along the moldparting line as the sections close on the parison. Thus, the parisonfrequently is not fully engaged by such a projection and often slipsinto the body of the mold cavity under the influence of gravity, or ispushed thereinto by the action of the neck finishing mandrel advancinginto the open ended parison. In addition, since these techniques dependon maintaining an open end on the portion of the parison defining thearticle neck, they of course are not applicable to blow molding systemswherein both ends of the parison are pinched shut on closing the moldsections, and the thus enclosed parison then expanded via fluid issuingthrough a hollow needle which has pierced the parison wall.

SUMMARY OF THE INVENTION Now, however, there has been developed a noveland highly versatile technique for finishing the neck portion of a blownhollow article which overcomes the previously noted deficiencies of theprior art.

Accordingly, it is a principal object of this invention to provide animproved method for finishing blown hollow articles having waste flashattached to neck portions thereof.

Another object of this invention is to provide such a method whichprovides for firmly supporting the parison in the neck flash or moilarea during blowing, thus avoiding undesirable sagging of one end of theparison into the mold during neck forming.

Yet another object of this invention is to provide such a method whichis especially applicable to blow molding systems utilizing a hollowneedle to expand the parison, wherein both ends of the parison arepinched shut during mold closing.

An additional object is to provide such a method wherein the outersurface of the neck is dimensionally precisely formed by blowing at thesame time the remainder of the article is blown.

A further object of this invention is to provide such a method which isequally applicable toward forming an article in a right side up, upsidedown or any intermediate position.

An additional object of this invention is to provide means for carryingout the above objects which do not require relatively complicated highspeed rotary machinery.

Other objects of this invention will in part be obvious and will in partappear hereinafter.

These and other objects are accomplished in a method of finishing ablown hollow plastic article having waste flash attached to a neckportion which comprises establishing a difference in temperature betweenthe neck portion and the flash in the area immediately adjacent saidneck portion, the temperature of the neck portion being sufficiently lowas to resist substantial deformation on application of a force thereto,the temperature of the immediately adjacent flash portion being inexcess of that of the neck portion but below that at which the plasticis incapable of sustaining itsform, gripping the waste flash, relativelymoving the gripped waste flash and the article away from each other tosever the flash from the neck in the area of attachment of the flash tothe neck leaving an irregualr lip extending around the opening at theouter end of the neck, and then advancing a forming mandrel into saidopening to roll the lip forwardly toward the body of the article andoutwardly against the wall of the blown neck to form a smooth neckfinish on the article.

Severing of the flash is carried out after the neck portion of thearticle has been blown, either while still confined within the formingmold or while separately supported, preferably around the neck,downstream of the blow mold. The parison is well supported prior toexpansion by substantial frictional engagement with surfaces of the neckflash holding section during mold closing.

The apparatus includes an inwardly directed step in the blow mold at theend of the neck defining portion, and means for gripping the flash whichpreferably comprise a pair of opposing jaws which in closed positionform a chamber substantially conforming in surface contour to that ofthe neck flash, each of the jaws having a groove formed in its surfacefor accepting a portion of the neck flash on closing thereon.

BRIEF DESCRIPTION OF THE DRAWINGS In describing the overall invention,reference will be made to the accompanying drawings wherein:

FIG. 1 is a partially schematic, sectional, elevational view taken alongthe line 1 1 of FIG. 3 illustrating apparatus components of theinvention after formation of an article having waste flash attached tothe neck portion thereof;

FIG. 2 is an enlarged partial, schematic, elevational view of a portionof the apparatus depicted in FIG. 1 in slightly modified form;

FIG. 3 is a plan view of the apparatus of FIG. 1;

FIG. 4 is a sectional, elevational view illustrating the flash removalstep of the present invention;

FIG. 5 is an enlarged perspective view of the end of the article of FIG.1 after the step illustrated in FIG. 4;

FIG. 6 is an elevational sectional view showing a subsequent step in theprocess of the present invention;

FIG. 7 is a view similar to FIG. 5 illustrating the end of the articleafter the step of FIG. 6; and

FIG. 8 is a sectional elevational view of an important alternativeembodiment of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS Referring now to thedrawings, there is illustrated in FIG. 1, apparatus generally designated10 for forming a hollow thermoplastic article such as a bottle, having afinished neck. Apparatus 10 comprises a blow mold 12 having partiblesections 14a and 14b which in the closed position form a cavity 16, theperiphery of which conforms to theshape of the bottle. Cavity 16includes a neck defining portion 18 and, as illustrated in FIG. 2,

may include a neck flash holding cavity adjacent neck defining portion18. In FIG. 1, neck flash holding cavity 19 is alternatively illustratedas being within the neck flash gripping means to be described hereafterin more detail. Supporting ledge projects inwardly at the upper end ofneck flash holding section 19 or 20 FIGS. 1 and 2) a distance greaterthan that of step 22.

Means, typically illustrated as blow head 24 in FIG. 1, are provided forexpanding a heat softened thermoplastic parison outwardly against thesurfaces of article shape defining cavity 16 to form the article. Blowhead 24 (FIG. 1) is adapted to move over the open end of the enclosedparison after its disposition within mold 12 and has a passage 29extending therethrough which is connected at one end to a suitablesource of pressurized fluid, not shown.

Means (FIGS. 1, 3 and 4) generally indicated as 26 are provided forgripping the neck flash. In the embodiment of FIGS. 1, 3 and 4, thesemeans include a pair of opposing jaw portions 30a and 30b (FIG. 3) whichin closed position form the neck flash holding cavity of the assembly.In the embodiment of FIGS. 2 and 6, the neck flash holding section is anintegral part of the blow mold, separate means being necessary with suchan apparatus arrangement downstream of the blow mold for gripping theneck flash, such as those illustrated in FIGS. 1 and 4 as 26. Each ofjaws 30a and 30b has an outwardly extending recess, preferably in theform of a circular groove, typically illustrated as 32 in FIG. 4, formedin its surface for accepting a portion of the neck flash on closingthereon. Arm portions 27 connect at one end to jaws 30 and at the otherend to means 46 for displacing gripping means 26 with respect to thearticle neck to sever the neck flash from the article at step 22 in amanner to be hereafter described in more detail. These means 46 mayinclude fluid actuated pistons within cylinders 48 and 50 which haverods 52 pivotally connected at 54 to arm portions 27 of gripping means26. Such pistons function to move jaws 30a and 30b upwardly andoutwardly in an arcuate path as generally illustrated in FIG. 4 duringneck flash removal. Cylinder 56 enclosing a piston attached to rod 58which in turn is pivotally connected at 60 to the arm portion27associated with jaw 30b serves to move the latter in a horizontal planeinwardly and outwardly toward and away from the mold parting line in thedirection of arrow 62 so as to enclose one half of the neck flashportion prior to upward reciprocation of the jaws. Though duplicatecylinders may be used for such horizontal movement of jaws 30, asillustrated in the embodiment of FIGS. 1 and 3, only one may benecessary if mold opening and closingis accomplished by moving half 14btoward and away from half 14a while holding half 14a having horizontallyimmovable jaw 30a thereon stationary. Each of cylinders 48, 50 and 56are connected through suitable conventional conduits, valving andcontrol instrumentation well known to those skilled in the art to one ormore sources of pressurized fluid for actuating the pistons'within thecylinders at the desired points in the process.

Also included as part of apparatus 10 is a circular forming mandrel 64which is smoothly contoured without surface projections and inwardlytapered along its leading end 66 for entry into the neck of the articleafter removal of the neck portion in a manner to be shortly described inmore detail. Mandrel 64 is connected to reciprocating means 66 formoving it into and out of the neck of the article. Suitable conventionalactuating means, for example a fluid operated piston within a cylinder,may be provided as part of these means 66 and connected to rod 68.Heating means such as one or more electrically operated cartridge typeresistance heaters, (not shown) may be incorporated into mandrel 64 iffound necessary.

As illustrated in FIG. 4, gripping means 26, as well as a formingmandrel of the type depicted at 64 in FIG. 1, may be located downstreamof blow mold l2 and necessarily must be so located with the alternativeembodiment of FIG, 8. Under such circumstances, means 70 which mayinclude another pair of jaws, typically illustrated at 72, must beprovided for supporting the article 74. These means preferably engagethe article around the outside surface of the neck, as shown so as togrip the threads and support the neck to prevent the formed neck frombeingdistorted, deformed or otherwise adversely affected by the pullingforce during the flash removal operation.

In the embodiment of FIG. 8, the means for expanding the parisonincludes a hollow needle 34 situated in a bore in one of the moldsections 36 having one end opening into the neck flash holding section28 of mold 38. As also illustrated in this embodiment, the article beingexpanded in the blow mold may be cylindrical preform 40 for use as theworkpiece in a separate downstream forming process independent from thatoccuring in mold 38. In such a case, the shape of the cavity within mold38 defining the article includes a cylindrical portion 41 wherein thediameter when the sections are closed on each other is substantiallyequivalent to that of the neck defining portion 24 of the cavity. Eachmold half 36a and 36b in FIG. 8 has opposing compression edges 44 and 46at either end thereof for sealing each end of the parison shut onclosing sections 36 on each other.

In operation, a thermoplastic parison in heat softened condition isextruded in a conventional manner through an annular orifice in anextruder head. The size of the orifice or the conditions of extrusionare controlled such that the maximum diameter of the unexpanded parisonis less than that of any of the various cavity portions of the mold withthe exception of supporting ledge 25 in FIGS. 1 and 2. This is necessaryto avoid generating flash along the parting line of the mold sections asthey close on each other and which thereafter would necessarily have tobe removed. The length of the parison is in excess of that necessary toform the desired article, the surface of the latter being defined bythat of cavity 16 of blow mold l2. Mold sections 14a and 14b are thenbrought together to enclose and dispose the extruded parison within thearticle defining sections of the mold. In so doing, an end section 76 ofthe flash defining end portion thereof is firmly frictionally engagedoutside the portion of the parison defining the article, by ledge 25 ofeither the mold sections (FIG. 2) or the gripping jaws (FIG.1), sincethe diameter of the opening at ledge portion 25 is less than that of theoutside diameter of the parison. The parison is therefore firmlysupported within the mold sections at the portion thereof adjacent thatwhich will form the neck of the article. The other end in FIG. 1 issealed shut as a result of the closing movement of the mold sections soas to form tall 48 in a conventional manner and which may besnapped offrelatively easily after the article is formed. Blow head 24 is thenmoved over the open end of the thus enclosed parison and pressurizedfluid admitted through passage 29 into the parison to expand itoutwardly against the article defining mold surfaces, thus forming neck80 by blowing, as well as the associated body portion of the hollowarticle. As illustrated in FIGS. 5 and 7, the outer surfaces of thenecks of consecutively shaped articles including top face 83will alwaysbe accurately formed to the exact same dimensions as that defined by theopposing fixed mold surfaces, since formation is by blowing outwardlyagainst such surfaces. Alternatively, mandrel 64 may have a passage (notshown) formed therein which is as-.

sociated with a source of pressurized fluid, and which may be used toexpand the parison on reciprocation downwardly without requiring aseparate blowhead. Since step 22 prevents the portion of the parisondirectly opposite it from expanding outwardly to any great extent, athickened section 82 will be present in the plastic in the area of thejunction of the flash with the upper end of the neck after the parisonhas been expanded. Because the diameters of the molding surfaces oneither side of step 22 are greater than that at step 22, the parisonwall thickness on either side of this step accordingly will also be lessthan portion 82, as illustrated in enlarged detail in FIG. 2. Afterexpansion, the plastic is allowed to remain for a short time in contactwith the opposing molding surfaces, which in turn are kept at a reducedtemperature, for example by circulating a conventional cooling mediumthrough channels (not shown) just below the molding surfaces. This timemust be sufficient to reduce the temperature of the neck portionsufficiently low as to resist substantial deformation on application ofa force thereto. The temperature of flash portion 82 opposite step 22,or in other words that portion of the flash immediately adjacent the endof the article neck, will also have cooled somewhat from its temperatureprior to expansion, in view of the cooling influence of the expandingfluid and the contact of its outer surface with that of step 22.However, for the periods of mold surface contact time underconsideration, for example on the order of from 3 to 10 seconds, thisminimum time being preferred to avoid uneconomical prolongation of themolding cycle, the temperature of flash portion 82 will be in excess ofthat of neck portion because of its greater thickness, but neverthelessbelow that at which the thermoplastic is incapable of sustaining itsmolded form. Also, the temperature of the flash in contact with thesurfaces of groove 32 adjacent step 22 will be incrementally less thanthat of portion 82 after the plastic has been in contact with suchsurfaces for said period of time, in view of the reduced wall thicknesscaused by thinning during expansion. When utilizing a step 22 projectinginwardly a distance of from 0.05 to 0.125 inch from surface 23 towardthe axis of cavity 16, the temperature of thickened section 82 for mostthermoplastic materials will be between 25to F. greater than that ofneck portion 80 of the article. This temperature difference wherein thatof the portion of the flash immediately adjacent the neck whereseveranceis to occur is greater than that of the adjacent neck is important. Thisis so because if the temperature of this immediately adjacent neck flashportion is reduced essentially to that of the neck, or in other words tothat at which the plastic will not substantially deform when stressed,the surface in the area of severance after removal of the flash will beextremely jagged, and will not deform in the desired manner under theinfluence of the subsequently entering forming mandrel. On the otherhand, if the temperature of the neck is the same as that of the hotimmediately adjacent flash portion, the blown neck finish willundesirably deform and distort substantially when the adjoining flash ispulled away. Though this temperature differential is illustrated in thepreferred embodiments as being established during the molding operation,it is within the purview of the invention to provide for reheating theflash in the area adjoining the neck in those situations where thearticle and adjoining neck flash have been allowed to cool sufficientlyas to set the plastic completely.

After the temperatures of the various sections of the end of the parisonhave reached the just described desired levels, and while the expandedparison is still confined within mold 12, flash portion 77 is moved awayfrom neck portion 80 to tear flash portion 77 away from neck 80 atthickened section 82, thereby leaving an irregular lip illustrated at 84in FIG. extending around the inner surface of neck portion 80, in thearea of prior severance. Such relative movement is accomplished in theillustrated embodiment of FIGS. 1, 3 and 4 by energizing the pistonswithin cylinders 48 and 50 so as to reciprocate jaws 30a and 30bupwardly away from mold enclosed neck portion 80, thereby tearing flashsection 77 away about step or edge 22.

Thereafter, while the temperature of the material now defining irregualrlip 84 is still sufficiently high to permit deformation of the plastic,tapered mandrel 64 is caused to advance into the open end of the articleneck to initially displace or roll lip 84 downwardly as a result of itscontact with the smooth tapered end 64 of the mandrel, and thenoutwardly against the inner wall of the previously blown neck as aresult of contact of the downwardly rolled lip with the increaseddiameter portion of mandrel 64 as the latter proceeds further into theneck, thereby finishing the upper end of the neck portion of the articlesmoothly as illustrated at 86 in FIG. 7. To accomplish this finishingfunction, as indicated in FIG. 6, the maximum diameter of mandrel 64should be slightly less than the diameter of step 22 by an amount on theorder of the thickness of that portion 82 of the parison opposite step22 after expansion. Mandrel 64 is then reciprocated upwardly out of theneck portion of the article, sections 14a and 14b are caused toseparate, and the piston 58 within cylinder 56 is caused to moverearwardly so as to draw jaw 30b away from jaw 30a, thereby allowing thearticle with the finished upper end to fall away from the blow mold. Asubsequently extruded parison formation is then disposed between themold halves and section 14b and jaw 30!) caused to move towardsection14a and jaw 30a respectively so as to enclose the next parison forcommencement of a subsequent cycle. I

The embodiment of the invention of FIGS. 2 and 4 illustrates the neckfinishing concept of the invention as occuring downstream of mold 12 orin other words after the blown article with attached flash has beenremoved from the mold. In such instances, the flash holding cavity isformed as an integral part of mold 12 as illustrated in FIG. 2, and thegripping means, otherwise similar to that of FIG. 1, are positioned soas to close around the outer surface of the flash after ejection fromthe mold as illustrated in FIG. 4. Prior to reciprocating the grippingmeans, the article is held in a fixed position, preferably by means 70frictionally engaging the formed outer neck surface. The forming mandrel64 is thereafter advanced into the open end of the article neck in thepreviously described manner. In this embodiment, the cavity 87 withingripping means 26 may be designed to be slightly smaller in size thanthat defined by the flash being removed in order that the jaws actuallysqueeze and compress the plastic when closed on the flash. Also, blownflash projection 89 serves to enhance the gripping action when thecooperating jaws are closed around the flash.

In the embodiment of FIG. 8, flash portion 88 is pierced with hollowneedle 34 after disposition of the parison within mold sections 36a and36b and pressurized fluid then introduced through the hollow needle intothe parison to expand it into the shape of cylindrical preform 40, or toany other desired article shape. In this embodiment, since both ends ofthe parison are pinched shut between compression edges 44 and 46 of moldsections 36a and 3612 during mold closing, it obviously is necessary totear the flash away from the neck downstream of the blow mold, asillustrated in FIG. 4. Otherwise the process is the same as that justdescribed.

The versatile process of the present invention is applicable to systemswhere extrusion is either in the upward, downward or any intermediatedirection. It is likewise applicable in right side up forming of thearticle as well as upside down forming, i.e., wherein the neck portionof the article is either above or below the base when enclosed withinthe mold. When extruding downwardly and forming in an upside downarticle position, the flash attached to the neck is represented by aportion of the leading end of the parison being extruded whereas withthe same direction of extrusion in right side up forming, the flash isrepresented by a portion of the trailing end of the parison beingextruded. The reverse is true when extrusion is in the upward direction.

Though the flash gripping portion of the apparatus of the invention hasbeen illustrated as including jaws which close around the outer surfaceof the flash, it is obvious that other gripping means might be utilized.Such means might include a threaded rod for insertion into the flashthrough the open end of the parison a distance sufficient to engage theinner surface thereof especially along molded threads in the plastic.During cooling the polymer will shrink and firmly grip the outer surfaceof the rod, and the flash may then be removed by pulling the rod withthe plastic impaled thereon away from the neck. The tapered formingmandrel would of course then be inserted into the neck to smooth theinner surface in the manner previously described. The preferred grippingmeans, however, in-

clude jaws closing on the outer surface of the flash, especially whenblowing systems of the type illustrated in FIG. 8 are used wherein theportion of the parison adjacent the neck of the article is sealed shutduring closing movement of the mold sections.

Though the neck portion of the article of the present invention has beenillustrated with threads in FIG. 5) formed on its outer surface forcooperating with those on a closure, other forms of closure cooperatingprojections molded by means of appropriate conforming cavities in theneck defining portion of the mold may be used. For example, in additionto those necessary to accommodate a threaded closure, lugs or rings foraccepting a roll on or crown closure or any combination of these on asingle neck are considered to be within the purview of the presentinvention. Also, in certain situations, it may not be necessary toemploy .any closure mating projections at all on the outer surface ofthe neck, for example, when the neck of the article is to remain open oris to accept a closure sealing on the inner surface of the finishedneck.

The above description and particularly the drawings are set forth forpurposes of illustration only and are not to be taken in a limitedsense. Various modifications and alterations will be readily suggestedto per-. sons skilled in the art. It is intended, therefore, that theforegoing be considered as exemplary only and that the scope of theinvention be ascertained from the following claims.

What is claimed is:

9 10 l. A method of finishing a blown hollow thermoplasd. advancing aforming mandrel into said opening to tie article having waste flashattached to a neck portion roll said lip forwardly toward the body ofthe article which comprises: and outwardly toward the wall of the blownneck a. establishing a difference in temperature in the to f a th k fi ih on h i l forming Q y l neck PQ 2. The process of claim 1 wherein saidarticle is a botflash portion ad acent said neck portion which is tle"thicker than that of Said neck portion the tempera 3. The process ofclaim 2 which includes the step of zg f g ghi fii z ggg g g g g :9: g?removing the bottle from a mold prior to severing the a Orma n pp a loflash from the neck.

a force th-ereto and the temperatu-re of Said thick- 10 4 The rocess ofclaim 1 wherein said article is a c ened portion being 25 to 100F. inexcess of that l p f Y y of the neck portion but below that at which them pre plastic is incapable of sustaining its form;

gripping the waste fl h; from the neck after the article is formed andwhile it is c. relatively moving the gripped waste flash and the mformmg mold; h

arti l aw f m h th t sever h fl h fr 6. The process of claim 1 whereinsaid article 15 fixed the neck in the area of th thi k n d ti l inposition and severing is accomplished by pulling the ing an irregularlip extending around the opening flash away from the fixedly positionedarticle. at the outer end of the neck; and then g 5. The process ofclaim 1 wherein the flash is severed

1. A method of finishing a blown hollow thermoplastic article havingwaste flash attached to a neck portion which comprises: a. establishinga difference in temperature in the forming cavity between the neckportion and a flash portion adjacent said neck portion which is thickerthan that of said neck portion, the temperature of said neck portionbeing sufficiently low as to resist substantial deformation onapplication of a force thereto and the temperature of said thickenedportion being 25* to 100*F. in excess of that of the neck portion butbelow that at which the plastic is incapable of sustaining its form; b.gripping the waste flash; c. relatively moving the gripped waste flashand the article away from each other to sever the flash from the neck inthe area of the thickened portion leaving an irregular lip extendingaround the opening at the outer end of the neck; and then d. advancing aforming mandrel into said opening to roll said lip forwardly toward thebody of the article and outwardly toward the wall of the blown neck toform a smooth neck finish on the article.
 2. The process of claim 1wherein said article is a bottle.
 3. The process of claim 2 whichincludes the step of removing the bottle from a mold prior to severingthe flash from the neck.
 4. The process of claim 1 wherein said articleis a cylindrical preform.
 5. The process of claim 1 wherein the flash issevered from the neck after the article is formed and while it is stillin a forming mold.
 6. The process of claim 1 wherein said article isfixed in position and severing is accomplished by pulling the flash awayfrom the fixedly positioned article.